#!/usr/bin/node

const Readable = require('stream').Readable;

let rs = new Readable(),
    c  = 'a'.charCodeAt(0);//转为ASCII码

rs._read = () => {
  rs.push(String.fromCharCode(c++));
  if(c > 'z'.charCodeAt(0)) rs.push(null);

};


rs.pipe(process.stdout);
